Apparatus for attaching zippers to plastic footwear



May 16, 1961 G. F. cLAsoN 2,984,287

APPARATUS FOR ATTACHING ZIPPERS TO PLASTIC FOOTWEAR Iig.

Ied June 26, 1958 INVENTOR Georqe F Clason ATTO R N EY APPARATUS FOR ATTACHING ZIPPERS T PLASTIC FOOTWEAR George F. Clason, Pawtucket, RJ., assignor to Scovill Manufacturing Company, Waterbury, Conn., a corporation of Connecticut Filed June 26, 1958, Ser. No. 744,873

3 Claims. (Cl. 154-42) My invention relates to an improved apparatus for attaching zippers to plastic footwear and especially to overshoes of the so-called slush molded type consisting of vinyl chloride or a plastic having similar characteristics. Such plastic footwear of the slush molded type has come into wide use in recent years but one of the objections to such overshoes as commonly made, is that the upper of the shoe cannot be neatly tted to the wearer. The upper is usually made large enough to allow the foot to be inserted in the overshoe and is commonly fastened by a single strap or button.

In order to obtain a neatly tting overshoe of this type, it has long been recognized that it would be desirable to fasten the overshoe by a zipper along a front opening. Due to many problems and requirements, however, previous attempts along this line have not been successful. Such problems and requirements include the necessity for a water-proof gusset to underlie the front opening, the fact that the zipper cloth tapes must be virtually welded to the edges of the opening so that the strength of the fastening will approach that of the strength of the material of the overshoe; the fact that the fastening should assume a slight curve over the instep portion; and the fact that the thickness of the material of the boot is greater than the thickness of other types of garments to which the zippers have been applied by a heat-sealing process.

The general object of my invention, therefore, is to provide an improved apparatus which will solve the problems involved and full the various requirements. A further object of the invention is to provide such an improved apparatus capable of employing the so-called electronic or high frequency heating to firmly attach and seal together the gusset, the zipper tapes and the material of the overshoe along the sides of a front opening. Other objects and advantages of the invention will hereinafter more fully appear.

In the accompanying drawings, I have shown for the purpose of illustration, one embodiment which my invention may assume in practice. In these drawings:

Fig. l illustrates an overshoe made according to my improved apparatus;

Fig. 2 is a side view of the apparatus indicating an intermediate process;

Fig. 3 is also a side view of the apparatus with a portion broken away and illustrating a later step in the process;

Fig. 4 is a perspective view of the bottom template die;

Fig. 5 is a perspective view of the upper die in inverted position; and

Fig. 6 is an enlarged cross section on line 6*6 of Fig. 3.

The finished overshoe 10 has a front opening 11 curving slightly over the instep portion with a suitable design around the opening, including in this instance, the raised portions or projections 12. The finished overshoe has a gusset 13 of flexible material and a zipper fastener consisting of a pair of cloth tapes 14a, the rows of metallic States Patent O fastener elements 14 on the adjacent edges of the cloth tapes and a slider 15. The gusset and zipper fastener are not visible in Fig. l but the construction and arrangement of these parts can be understood from Figs. 2, 3 and 6.

The bottom template die shown in Fig. 4 is supported by a suitable over-hanging arm 16 projecting from the frame of a press. The template die has a supporting plate 17 which is of metallic material having good electrical conducting properties, such as brass, and is provided with suitable means for attaching it to the arm 16. Overlying the central portion of the supporting plate 17 is a strip 18 of heat-resistant plastic material having a smooth upper surface. The material of this strip in addition to being heat-resistant, should be one which, when subjected to high frequency current, will not overheat. It also acts as a heat insulator to prevent rapid conduction of heat to the brass plate 17. I have found that a thin strip of melamine resin reinforced with glass fabric is suitable for this purpose. The strip 18 is held in place upon the plate 17 by bordering or locating strips 19 and 20 of suitable material, preferably having good electrical insulating quality such as hard ber, which bordering strips are secured to the plate by screws 21. The inner edges of these bordering strips are spaced apart a distance corresponding to or slightly greater than the overall width of the zipper fastener and serve to locate the outer edges of the gusset.

Underlying the supporting metal plate 1.7, and attached thereto, there may be a further strip 22 of suitable material, such as hard ber for its electrical and heat insulating properties. This strip 22 extends the full width of the plate 17 but, as seen in Fig. 4, the ends of the plate project beyond the ends of the strip 22.

The template die also carries a retaining finger 23 which may be of steel resiliently mounted on plate 17 beyond the inner end of the strip 18 as by means of a screw 24 surrounded by a coiled spring 25, and the slightly upturned end 26 of the spring finger is adapted to bear against the zipper elements 14. As shown in Fig. 4, this finger 23 is swung out of the way, but it will be understood that after the gusset and zipper are in position on the template die it may be placed between the locating pins 27 so that it extends centrally of the plate 17. The template die has a longitudinally extending slot 28 closed at both ends, which slot is of a length and width corresponding to the metallic components of the particular zipper fastener to be attached to the overshoe. At its inner end, the slot has a widened portion 29 to accommodate the underside of the slider 15 of the zipper fastener and an extension 30 at this end of the slot may accommodate the edges of the folded gusset. It will be understood that this slot 2S extends vertically through the strip 18, plate 17, the bottom insulating strip 22 and also through the arm 16.

The upper die member 31 is attached to a vertically movable head 32 of the press, preferably with a plate 33 between the die and head 32, which plate 33 is somewhat longer than the die so that the die can be removed and easily replaced with a somewhat longer die to accommodate a longer overshoe opening and longer zipper.

The construction of this die as seen in Figs. 5 and 6 utilizes as the principal part, a metallic block 3'4 having a ange 35 at the top to tit against the plate 33 by which it is carried. The material of this die block 34 must have good electrical conducting properties and is preferably made of brass. The bottom surface 36 of the upper die member may be described as a U-shaped pressing surface and is so dimensioned as to apply heat and pressure along the sides of and around the bottom of the zipper in a U-shaped area which is substantially wider than the metallic components of the closed zipper to prevent sealing of the plastic material too close to the metal elements of the zipper. Inside the U-shaped area, the die block has a deep central groove 37 in which is tightly fitted an insert 3S of heat-resistant non-conducting material, such as Bakelite. A central groove 39 is formed in this insert, opening downwardly toward the Working surface of the upper die, which groove is somewhat wider than the slot 23 in the template die. The lower edges of the insert provide a narrow U-shaped supplemental pressing surface 40 which is set slightly inwardly from the plane of the main pressing surface 36. It will also be noted that the edges of the insert providing the Ushaped surface 40 are spaced away from the adjacent metal around the insert leaving a shallow groove 41 between the main metal pressing surface and the supplemental pressing surface of the insert. It will alsobe noted that the die block has a series of recesses 42 opening through the pressing surface but within the confines of the area of such surface which may be of any desired shape providing a pleasing design around the front of the -boot as appears in Fig. 1. These recesses also have an important function in the apparatus which will be referred to later on.

In carrying out the process of attaching zipper fasteners in a plastic overshoe, a generally triangularly-shaped gusset of thin flexible water-proof material, preferably a vinyl plastic, is folded along the median line and inserted through the slot 28 in the template die. Then the edges of the gusset are laid over on opposite sides of the slot against the upper surface of the strip 18 with the edges of the gusset located against the bordering strips 19 and 2t?. Next, the zipper is laid upon the gusset with the metal portions of the zipper projecting into the slot 28 and the slider into the wide portion of the slot 29. Then the spring finger 23 is swung into position so that its end 26 bears on the metal chain of the zipper to retain the parts thus temporarily assembled. Next, the overshoe, which at this time has an uninterrupted solid front, is pushed over the entire assembly so that the zipper fastener aligns with the central front part of the upper boot. Then the head 32 is lowered against the outer surface of the boot and pressure exerted thereon, preferably by a compressed air cylinder. Simultaneously, current from a suitable high frequency generator flows into the upper die block which serves as an electrode, through the material of the boot, zipper tapes and gusset into the supporting plate 17. This plate 17 may connect Iback to the generator or may be grounded to the machine.

During this operation, the high frequency current is confined to the U-shaped area of the main metal pressing surface of the upper die block so that the plastic material of the overshoe and gusset in this U-shaped area is heated to the fusing point. Since the material of the overshoe is relatively thick, the pressure is continued so that the thickness in this heated U-shaped area is reduced sufficiently and the heating continued to a point where a thorough welding of the material through the cloth tapes of the Zipper is accomplished.

It may also be mentioned that the Zipper tapes themselves in the area where they are to be attached may be initially impregnated with a plastic material which will assist in the bonding or welding operation. During the process, the metal parts of the zipper and the retaining finger 2.3 are shielded by the insert 40 of insulating material.

In view of the `fact that the thickness of the overshoe material is substantially reduced, provision is made for the excess material. MostV of such excess material is allowed to flow into the recesses 42 resulting in the projections 12 which are substantially thicker than the original wall of the overshoe. Other excess material flows into the groove 41 so as to form a bead `43 as indicated in Fig. 6.

in the regions of the thicker portions, namely, the projections 12 and the bead 43, there is no firm bonding to the zipper tapes, and the bead 43 makes a comparatively stiff junction between the sealed portion of the upper and the part between the sealed portions so that after the boot is slit, the resulting lips will tend to hug more closely to the zipper to conceal same, particularly when under some tension while the overshoe is being worn. To complete the process, it is only necessary to raise the top die and pull the boot from the template die and slit the overshoe along the median line of the zipper. Since the gusset is sealed tightly along the sides and around the bottom of the opening, the overshoe is made waterproof.

The template die and mold herein shown are intended to seal the zipper in a straight line down the front of the boot. In the process, however, there is no rigidity imparted to the assembly so that when the overshoe is placed upon a foot, the fastener will assume the curve of the instep. If desired, however, the template die and upper die could be modified so as to seal the fastener along a curve.

While I have shown and described one embodiment which my invention vmay assume in practice, it will be understood that modifications and variations within the scope of my invention as defined in the appended claims will occur to those skilled in the art.

What is claimed:

l. In an apparatus of the class described for attaching zippers to plastic footwar, a template die having a supporting member of metallic-conducting material and a strip of heat-resistant plastic material attached to the upper surface of said member, said template die having a longitudinally extending slot through said strip and supporting member whose width and length correspond to the width and length of the metal portions of a closed zipper to be attached including a widened portion at one end of the slot to accommodate the zipper slider, and an upper metallic die member having a U-shaped pressing surface adapted to press material against said strip in a U-shaped area along the sides and around one end of the slot, which area is spaced a substantial distance from the slot, an insert of non-conductive material fixed in said upper die member and surrounded by said pressing surface, said insert having a central groove adapted to register with said slot in the template die and opening toward the plane of said pressing surface, wherein said upper die has a series of recesses opening through said U-shaped pressing surface but within the confines of the area of such surface.

2. in apparatus of the class described, the combination of claim l wherein the portion of said upper die insert around the central groove presents a supplemental pressing surface separated from the main metallic pressing surface by a narrow U-shaped groove, which supplemental pressing surface is also set slightly inwardly from the plane of the main pressing surface.

3. In apparatus of the class described, the combination of claim l and a finger resiliently mounted on the ternplate die beyond one end of the slot adapted to overlie and bear against the zipper for holding the zipper in position.

References Cited in the file of this patent UNITED STATES PATENTS 1,842,719 Dunker Jan. 26, 1932 2,515,050 LHallier July 11, 1950 2,674,559 Zobel Apr. 6, 1954 2,701,222 Hetzel et a1. Feb. 1, 1955 

